The defense debate in the first four years of the Reagan administration was less about defense than about the size of the defense budget. The president asked for large increases each year, and mostly got them. The amount of money made available was such that the administration was largely freed of the necessity to choose among strategies and weapons. It was able to have them all. The administration's critics in Congress were freed of the same necessity. The size of the budget was their rallying point and target; they argued simply that it should be less.

Now the terms of debate have changed, because this year the critics finally won. The defense appropriations bill is still pending, but the most it appears that the Pentagon will be granted is a 3 percent increase in spending authority -- enough to cover inflation -- and the House would give it no increase at all. Partly because of the deficit, partly for other reasons, the enthusiasm for defense increases that marked the first Reagan term has flagged. The budgets for the next several years will be tighter.

This puts on both sides in the debate the unaccustomed obligation to decide and spell out what to discard. A new report from Georgetown University's Center for Strategic and International Studies suggests that the Pentagon, at any rate, will make these decisions the wrong way. The report's steering group was made up entirely of retired general officers and former defense officials. It says that:

To extend the present buildup the Pentagon's budget would have to grow 5 percent per year beyond inflation. But Congress is unlikely to approve for 1987 and 1988 even the 3 percent after-inflation increases contemplated in the congressional budget resolution, to which the Pentagon has already accommodated itself. The historical growth rate of 1.5 percent is a likelier outcome.

The Pentagon's tendency will be 1)not to plan for this level in advance, lest its plans be mistaken for acquiescence, 2)to distribute the cuts from present expectations proportionally among the rival services, and 3)to retain present force structures -- numbers of tanks, divisions, fighter wings, carrier battle groups -- and absorb the cuts in the "readiness" side of the budget.

But proportional cuts among the services, while easiest in terms of interservice politics, would be "the worst of all the alternatives" in that they would weaken U.S. conventional forces everywhere instead of selectively. Preserving force structure at the expense of readiness would also be wrong: "the participants generally agreed that a ready force, sustainable and mobile in conflict, was preferable to a larger, hollow force if resources forced these difficult trade-offs."

The worried alumni did not just admonish the Pentagon, however. Their report said that a smaller defense budget would inevitably mean the writing off of competing U.S. geopolitical goals, and would require a reduction in commitment either to Europe or in Asia. The extent to which this is true is disputed, but those who would cut the budget on fiscal or fairness grounds must speak to the strategic consequences too. This is central to what must come next on defense.